Highly textured crystalline films enabled by supercooling for short-channel vertical organic field-effect transistors exhibiting high on/off ratios

Vertical organic field-effect transistors (VOFETs), where the channel length is determined by the thickness of the semiconductor, show great potential for future electronic devices. However, fabricating high-performance VOFETs with channel lengths of just a few tens of nanometers remains challenging, because ultrathin active layer is prone to leakage currents and electrical shorting. Here, a supercooling-assisted crystallization strategy is proposed to fabricate highly textured ultrathin C8-BTBT crystalline films for short-channel VOFETs. Compared with conventional slow-crystallization methods, this strategy stabilizes the preferred molecular orientation during crystallization, yielding highly ordered crystalline films with improved molecular tilt and enhanced vertical charge transport. By integrating these films with a self-assembled graphene source electrode, VOFETs with channel lengths as short as 25 nm were successfully fabricated. The optimized devices with a 50 nm-thick semiconductor layer exhibited an on/off ratio close to 109 and a current density of 137.15 mA cm⁻2. Furthermore, the excellent film uniformity enabled consistent device arrays with a density of 2500 units cm⁻2, providing a feasible route toward high-density, solution-processed small-molecule organic integrated circuits.